Hearing devices are wearable hearing apparatuses which are used to assist the hard-of-hearing. In order to accommodate numerous individual requirements, various types of hearing devices are available such as behind-the-ear (BTE) hearing devices and in-the-ear (ITE) hearing devices, for example also concha hearing devices or completely-in-the-canal (ITE, CIC) hearing devices. The hearing devices listed as examples are worn on the outer ear or in the auditory canal. Bone conduction hearing aids, implantable or vibrotactile hearing aids are also available on the market. The damaged hearing is thus stimulated either mechanically or electrically.
The key components of hearing devices are principally an input converter, an amplifier and an output converter. The input converter is normally a receiving transducer e.g. a microphone and/or an electromagnetic receiver, e.g. an induction coil. The output converter is most frequently realized as an electroacoustic converter e.g. a miniature loudspeaker, or as an electromechanical converter e.g. a bone conduction hearing aid. The amplifier is usually integrated into a signal processing unit. This basic configuration is illustrated in FIG. 1 using the example of a behind-the-ear hearing device. One or a plurality of microphones 2 for recording ambient sound are built into a hearing device housing 1 to be worn behind the ear. A signal processing unit 3 which is also integrated into the hearing device housing 1 processes and amplifies the microphone signals. The output signal for the signal processing unit 3 is transmitted to a loudspeaker or receiver 4, which outputs an acoustic signal. Sound is transmitted through a sound tube, which is affixed in the auditory canal by means of an otoplastic, to the device wearer's eardrum. Power for the hearing device and in particular for the signal processing unit 3 is supplied by means of a battery 5 which is also integrated in the hearing device housing 1.
Noise reduction algorithms are used to suppress interfering noises and/or to reduce them in terms of their level. In particular, very quiet noises are then often lowered to completely below the threshold of hearing. This results in an unnatural auditory impression. However, it is desirable for a natural auditory impression for quiet noises also not to get completely lost, i.e. not lowered to below the threshold of hearing.
In order to solve this problem, the possibility exists of deactivating the noise reduction in the case of quiet ambient levels. The manual deactivation of the noise reduction would be very impractical. With automatic deactivation, the problem nevertheless exists of determining the threshold at which the noise reduction is to be deactivated. In addition, a very unstable acoustic pattern results in the case of levels precisely around this threshold.
The publication EP 1 307 072 A2 discloses a method for operating a hearing device, in which interfering acoustic effects caused by activation and deactivation processes are to be avoided. The activation and deactivation of algorithms, which refer to the reduction of interference signals, is also referred to here in particular.